The model is the 1048 which produces 600 litres per hour in quiet and efficient fashion. In terms of overall design I like the clean lines and simple generator look. Under the hood is no less impressive with a centrifugal impeller mechanism made from hard wearing ceramic parts.

In engineering terms a centrifugal arrangement is preferable as it isn’t stressed by restrictions in flow like propeller drive arrangements, which I gather does make the latter prone to burn outs.

The upshot is the new pump now whizzes the entire 2.5 litre reservoir capacity via the CPU and GPU a theoretical 4 times per minute. I say theoretical because some reduction in flow must occur due to the restrictions of the two blocks, however in comparison to the stock pump this is producing twice the flow.

I’ll just add something here about the pump ‘head’ which is the limiting vertical distance above or below your system. Sometimes also called ‘lift’, I tend to think of this as similar to torque in engines. The Zalman pump had a head of 0.5m, in comparison the 1048 is 1.5m, therefore giving a threefold increase.

Points to note

The pump is NOT self priming. To prime it hook up to the reservoir (horizontal adaptor) and prior to connecting power, suck briefly on the pressure outlet (vertical adaptor) until coolant flows to the pump and is visible. Alternatively if you simply position the pump below the reservoir, gravity will do the job just as well.
In any event the pump must not run dry.

When I initially started the pump I was most dismayed at the noise it made. It sounded like there were ball bearings in the liquid rattling through it loudly.

Switching it off and checking I found no faults so tried again. I left it a while this time and it gradually became quieter until after 5 minutes was entirely silent. I surmised it was trapped air bubbles in the system causing some cavitations until they dissipated.

I noticed PTFE tape wasn’t mentioned, or included, for the two hose adaptors. Knowing it’s good practice I applied some to the threads.   

Build
Zalman helpfully provide a PDF describing removal of the integral pump and installation of an external replacement, which is part of the product instruction manual – available here.

In short you remove the Reserator base, detach the pump and power switch and seal the revealed power conduit with a sealing bolt. It’s very simple.

The useful inclusion of this bolt in the original package and the instructions leads me to suspect Zalman expect upgrading the pump to be a popular modification. There’s no doubt in my mind that replacing the matchbox sized original with something more substantial and accessible is the way to go.

The only small difficulty I had was removing the sink base from the radiator. This was on tight! It required removal of the plastic hose couplings so they wouldn’t be damaged, copious dousing with WD40 (penetrating fluid) and some serious encouragement with a rubber mallet.

Refitting I renewed the PTFE tape on all the threads. The pump power switch was not identical to the instructions being permanently soldered instead of screwed so I just cut the cable.

The diagrams are crystal clear like this example, indicating the recommended site of the external pump:

For extra peace of mind I’ve added two mini jubilee clips over the hose connections to the pump. Probably unnecessary as they didn’t leak without but it can’t hurt.

This is it all complete. Once I’m happy there are no problems the pump will neatly tuck away behind.

Next, some results.